Enable compositing of scrolling content on low-DPI when LCD text will be maintained

third_party/WebKit/LayoutTests/paint/invalidation/repaint-composited-child-in-scrolled-container-expected.txt

 {
   "name": "Content Root Layer",
   "bounds": [800, 600],
   "children": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
-      "paintInvalidations": [
-        {
-          "object": "LayoutBlockFlow (positioned) DIV id='outer'",
-          "rect": [8, 293, 285, 15],
-          "reason": "scroll"
-        }
-      ],
       "children": [
         {
-          "name": "Ancestor Clipping Layer",
+          "name": "LayoutBlockFlow (positioned) DIV id='outer'",
           "position": [8, 8],
-          "bounds": [285, 285],
+          "bounds": [300, 300],
           "shouldFlattenTransform": false,
+          "drawsContent": true,
+          "backgroundColor": "#0000FF",
           "children": [
             {
-              "name": "LayoutBlockFlow (positioned) DIV id='container'",
-              "position": [-315, 0],
-              "bounds": [600, 600],
-              "contentsOpaque": true,
-              "drawsContent": true,
-              "backgroundColor": "#FF0000",
-              "paintInvalidations": [
+              "name": "Scrolling Layer",
+              "bounds": [285, 285],
+              "shouldFlattenTransform": false,
+              "children": [
                 {
-                  "object": "LayoutBlockFlow DIV id='inner'",
-                  "rect": [0, 0, 600, 600],
-                  "reason": "style change"
+                  "name": "Scrolling Contents Layer",
+                  "bounds": [650, 600],
+                  "contentsOpaque": true,
+                  "drawsContent": true
+                }
+              ]
+            },
+            {
+              "name": "Overflow Controls Host Layer",
+              "bounds": [300, 300],
+              "children": [
+                {
+                  "name": "Horizontal Scrollbar Layer",
+                  "position": [0, 285],
+                  "bounds": [285, 15],
+                  "paintInvalidations": [
+                    {
+                      "object": "Horizontal Scrollbar Layer",
+                      "rect": [0, 0, 285, 15],
+                      "reason": "full"
+                    }
+                  ]
+                },
+                {
+                  "name": "Vertical Scrollbar Layer",
+                  "position": [285, 0],
+                  "bounds": [15, 285]
+                },
+                {
+                  "name": "Scroll Corner Layer",
+                  "position": [285, 285],
+                  "bounds": [15, 15],
+                  "drawsContent": true
                 }
               ]
             }
           ]
+        },
+        {
+          "name": "LayoutBlockFlow (positioned) DIV id='container'",
+          "position": [-307, 8],
+          "bounds": [600, 600],
+          "contentsOpaque": true,
+          "drawsContent": true,
+          "backgroundColor": "#FF0000",
+          "paintInvalidations": [
+            {
+              "object": "LayoutBlockFlow DIV id='inner'",
+              "rect": [0, 0, 600, 600],
+              "reason": "style change"
+            }
+          ]
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
-      "object": "HorizontalScrollbar",
-      "reason": "scroll"
-    },
-    {
       "object": "LayoutBlockFlow DIV id='inner'",
       "reason": "style change"
     }
   ]
 }